Advanced Bipolar Plate for a Unitized Regenerative Fuel Cell

An advanced composite bipolar plate is described for a unitized regenerative fuel cell and electrolyzer system that operates on pure feed streams (H-2/O-2 and water, respectively). The composite bipolar plate can greatly simplify "closed-loop" unitized fuel cell/electrolyzer power systems, as it eliminates the need for saturators, a second stack, and water/gas phase separation equipment. It provides a substantial system improvement over current alkaline systems in that it allows for simple high pressure electrolyzer operation with a high differential pressure. Additionally, it allows for dead-ended H-2 and O-2 feed during fuel cell operation, eliminating parasitic pumping losses required for water removal in a conventional fuel cell. Results from a 50 cm(2) bench design are presented. Additionally, the composite bipolar plate has been used to deliver methanol vapor to a direct methanol fuel cell, resulting in a lower methanol concentration at the catalyst/membrane interface and reduced methanol cross-over.